1. Field of the Invention
The invention relates to a process for the production of bent or curved glass plates or panes with more markedly bent areas, and in particular bent automotive glass plates in which the glass plates are homogeneously heated in a continuous furnace to the bending temperature, are locally additionally heated with gas flames in the more markedly bent areas on leaving the continuous furnace and are subsequently bent.
2. Description of the Related Art
In a known process of this type there are provided in the last portion of the continuous furnace and above the glass plate conveying place movable gas burners whose movement is controllable independently of the movement of the glass plates and which follow the latter within the continuous furnace with the aid of a suitable movement means (EP 0 103 983). The glass plates are bent on a bending ring in the following bending station.
Following the additional local heating by gas burners in the known process during the travel of the glass plates up to the bending apparatus, there is a more or less pronounced temperature gradient in the glass plate surface. In order to ensure the desired local temperature increase at the time of the bending process, it is necessary to have a relatively strong additional heating. However, such a strong additional heating can lead to undesired deformations of the glass plates, which impair their optical characteristics.
In a process of the aforementioned type, it is also known to arrange stationary gas burners within the bending station (DE-25 40 603, DE-26 28 518). However, it is not possible to achieve an adequate local temperature rise solely with the aid of the devices described therein and the fuel gases used, because the short cycle times of the device required for economic reasons are not sufficient for the necessary temperature rise.